Passive Optical Networks

OADM, which was based on acousto-optic switches, at each network node, was

proposed. In [40], optical filters and OSWs were employed at ANs for wave-

length dropping and protection switching respectively. In [40, 41], an AWG add-

drop filter was employed as the OADM and a loopback circuit was implemented

to provide protection switching at each AN. However, these approaches still

required two working fiber paths to support both protection as well as bi-

directional transmission. In [42–46], single-fiber bidirectional SHR (Self Healing

Ring) networks were also reported. This could further reduce the system cost and

increase the fiber efficiency in SHR networks. In [47], an interesting star-ring-bus

dense-WDM subcarrier-multiplexed network, with simple ...